1. Field of the Invention
The present invention relates to an optical disk for storing audio/video information or general data, and in particular, to an optical disk provided with a recorded area of a small diameter, in which the size of the display area for displaying letters, pictures, etc. on the disk is enlarged.
2. Description of the Prior Art
FIG. 4 is a schematic diagram showing the surface of a conventional optical disk such as a CD (compact disc) and a DVD (digital video disc) with a diameter of 12 cm. As shown in FIG. 1, the conventional optical disk comprises a center hole 12, a clamping area 13 outside the center hole 12, a lead-in area 14 outside the clamping area 13, a program area 15 outside the lead-in area 14, a lead-out area 16 outside the program area 15, and a narrow transparent area 17 between the lead-out area 16 and the circumference of the optical disk. In such conventional optical disks, even in the case where the diameter of the recorded area of a 12 cm optical disk fits in that of 8 cm optical disks, null data pits are formed on the 12 cm optical disk from a diameter corresponding to that of the recorded area of 8 cm optical disks to the maximum diameter to which recorded areas of 12 cm optical disks can be provided, and a reflective layer is also formed on the above area. Therefore, in conventional optical disks, discrimination of the diameter of the recorded area in appearance is difficult. In addition, the display area can be formed only on the one side of the disk.
As disclosed in JP-A-6-508712 (PCT), some types of optical disks are proposed in order to expand the display area of optical disks used for displaying letters, pictures, etc.
According to the optical disk disclosed in JP-A-6-508712 (PCT), in the case where the diameter of the recorded area of a 12 cm optical disk fits in that of 8 cm optical disks, audio information can be written in a recorded area from inside of the disk toward outside, for example, within a diameter of 70-80 mm, and a metallization area outside the recorded area within a diameter of 118 mm serves as the display area to which holograms or pictures are freely provided.
However, the holograms can be made on only the one side so that in the case where metallization process is utilized for displaying letters, pictures, etc. on optical disks, a plate for the holograms must be produced for every CD title and thus there exist problems of operation efficiency, cost, etc.
Moreover, when label design (display of contents, tune titles, trademarks, etc.) is displayed on a conventional optical disk, display of only one type of label design on one side of the optical disk is possible and display of different types of label designs on both sides of the disk is impossible.